1. Field of the Invention
The present invention relates to a method for image formation wherein an image is formed by an inkjet process on a textile fiber product which has been subjected to a fiber-modifying treatment and a textile fiber product obtained thereby.
2. Description of the Prior Art
In recent years, a method for image formation on a textile fiber product by an inkjet process has been developed with the advantage of obviation of the need for plate making.
When a dye is used as a colorant in an ink utilized in an inkjet process, it is necessary to change the dye (hence to change the ink containing the dye) is according to the kind of fiber, and problems arise from complex processes following inkjet printing, such as steaming, washing, soaping, and drying, and a tendency for increasing environmental loads.
Meanwhile, when using a pigment, which, unlike dyes, does not have substantivity for fibers, as a colorant in the ink, there are advantages in that unlike with dyes, textile fiber products of various fibers can be colored with a single kind of ink, although an binder is needed to bind the pigment to a fiber, and that the environmental load is low because of the obviation of the need for the steps of steaming and washing after printing.
However, when a pigment ink is inkjet-printed directly on a textile fiber product, the pigment ink penetrates the cloth product, which is configured with fiber, making it difficult to obtain high-density patterns, and the pigment ink undergoes migration, making it difficult to obtain brilliant images. For this reason, images formed using a pigment ink are likely to lack adequate concealing performance. Hence, when the textile fiber product to be printed has a color, pattern, and the like, the color, pattern, and the like on the back side appear at least to some extent on the image formed using the pigment ink; in this regard as well, expected brilliant images are unlikely to be obtained.
When the textile fiber product to be printed has a color, pattern, and the like, it is a common practice to form a masking layer that masks the color, pattern, and the like, and to form a desired image on the masking layer. However, when it is intended to form a masking layer on a textile fiber is product by an inkjet process using a white ink with concealing performance or the like, adequate concealing performance is unlikely to be obtained due to the penetration and migration of the white ink; therefore, it is difficult to form a desired brilliant image thereon.
Examples of past proposals concerning image formation by an inkjet process using an ink containing a pigment as a colorant include the techniques described in the references (1) to (3) below.
(1) JP 2004-276253 A
Described is a technique for generating a bleed-free good image of high image density by allowing a pretreating liquid for printing containing at least a water-soluble polyvalent metal salt, a surfactant, a high-boiling-point amine, a benzotriazole salt, and water to adhere to a recording medium such as paper for ordinary office work, and thereafter allowing an aqueous pigment ink to adhere thereto by an inkjet recording process.
(2) JP 4969578 B2
Described is a method for digital printing on a fabric, comprising:    (a) a step for pretreating a fabric with a pretreating liquid containing an aqueous polyvalent cationic salt solution,    (b) a step for digital-printing the pretreated fabric with an inkjet ink based on an aqueous white pigment, wherein the printed area is of substantially the same shape as that of a printed color image applied thereon, and    (c) a step for digital-printing the color image on the white ink using an aqueous color inkjet ink.
(3) JP 5337351 B2
Described is an inkjet printing method comprising applying a treating liquid containing a water-soluble polyvalent metal salt, a nonionic resin emulsion having a glass transition temperature of −30 to 0 degrees Celsius, and an aqueous medium to a printing region of a cloth, heating the cloth, printing a white ink for inkjet printing containing a white pigment on the region with the treating liquid applied thereto, and printing a chromatic ink for inkjet printing.
However, the proposals described in the aforementioned references (1) to (3) pose the problems shown below.
The technique described in the reference (1) mainly targets paper and plastic films as recording media. When it is used for a textile fiber product, which has rougher fiber texture than paper, the pretreating liquid is unlikely to adhere uniformly onto the fiber surface, and the inkjet ink penetrates easily in the fibers; therefore, it is difficult to form a brilliant image of excellent concealing performance.
The technique described in the reference (2) is a technique for printing a textile pretreated with a pretreating liquid containing an aqueous polyvalent cationic salt solution with an inkjet ink based on an aqueous white pigment, and printing an aqueous ordinary ink on the printed image, ensuring concealing performance by the ink based on the aqueous white pigment, and yielding a brilliant image; however, the binding of the fabric and the pigment in the ink is insufficient, and the fastness for a fabric is not considered to be adequate.
The technique described in the reference (3) is intended to perform printing with concealing performance and excellent durability by treating a cloth with a treating liquid containing a water-soluble polyvalent metal salt and a resin emulsion, and then printing a white ink for inkjet printing; however, the binding of the resin emulsion in the treating liquid and the white pigment in the ink is insufficient, and the fastness for a cloth is not considered to be adequate.
As stated above, when using a pigment as a colorant in forming an image on a textile fiber product by an inkjet process, it is unnecessary to choose a pigment according to the kind of fiber, and the steps are relatively simple; however, this method poses problems, including difficulty with the obtainment of brilliant images and inadequate quality in feeling and fastness of the textile fiber product with an image formed thereon.
For this reason, there is a demand for the development of a method for image formation on a textile fiber product by an inkjet process using an ink with a pigment as a coloring agent, which makes it possible to obtain a brilliant image of excellent concealing performance and a product with good image fastness and a soft feeling, and a textile fiber product obtained using the method.